ESA Headquarters1990 M Street, NWSuite 700 Scientific Reports Enhanced physical structure associated with Sabella and mimics increased nitrogen fluxes, community metabolism and reduced denitrification from 23 μmol m⁻² h⁻¹ to zero at densities greater than 25 m². Ecosystem Engineers maintain the health and stability of the environment they live in. Interactions between organisms are a major determinant of the distribution and abundance of species. 154, 84–93 (2015). Google Scholar. 144(5), 1029–1037 (2004). In all cases, fluxes of solutes were calculated as concentration change during incubation (µmol/L) times chamber volume (30 L), divided by elapsed incubation time (h) and area of sediment enclosed (0.25 m2). Other in, that destroy structure include bioeroders such as isopods (T. and Crooks 2007) and mitten crabs (Rudnick et al. Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA. J. Mar. Most refugia in rivers are characterized by extensive Trees are a good example, because as they grow, their trunks and branches create habitats for other living things; these may include squirrels, birds or insects among others. Evol. 7(1), 87–118 (2006). Lohrer, A. M., Cummings, V. J. Here we use an experimental density gradient of Sabella and mimics and examine shifts in flux rates and key fauna to test these three theoretical models of impact mechanisms. Reefs’ M. palmata population (demo) displays variations in: (a) abundance, (b) mean size, and (c) proportions of demographic categories. The variability of some population (demo) parameters of the gammarid amphipod Melita palmata was associated with contrasting habitat structures created by the non‐indigenous reef‐builder polychaete Ficopomatus enigmaticus in the Mar Chiquita coastal lagoon (37°40 S, 57°23 W, Argentina). Living oysters and their shells as sites of nitrification and denitrification. This is done by creating modifying and maintaining habitats. Howev, organisms not able to live within the dense mat matrix, such as bi, grass, the mussel can have detrimental effects likely related to both habitat, modification and competition for food (Reusch and Williams 1998; Crooks, understanding of the consequences of anthropogenic biological invasions, there, are other important implications of exotic engineers. quantitative predictions can be made related to biotic effects. 2001; Casas et al. Autogenic engineering is the alteration of physical aspects of the environment by the bodies of the engineers themselves (e.g., alteration of flow regimes by Sabella tubes or provision of habitat for other organisms), whereas allogenic engineering is the alteration of physical environmental properties via mechanical or chemical means (e.g., extraction of particulate material by Sabella)1.